Apple has made some changes to how iOS handles apps that wish to access users' music libraries, with iOS 10 now requiring your explicit permission before any app is allowed to interact with your music.
This new safeguard increases your privacy while ensuring that no app can silently analyze what's in your music library without you knowing it. Additionally, it makes it more difficult, if not downright impossible, for apps to potentially upload your music library to the cloud in order build a profile of your musical tastes for advertising purposes.